Does anyone have experience with Veritas Netbackup 3.4 for Solaris and a Breecehill Q6.210 DLT Library?

We have a Breecehill Q6.210 with 6 Quantum DLT 7000 drives in it. The first two drives are daisy chained to a NetApp 740. The second two are daisy chained to the robot, which is connected to a Sun 450, running Solaris 2.6. The third pair of drives are daisy chained to a NetApp 760.

The problem, is that when I come in every Monday morning, after the our Full backups are scheduled to run, 4 of the 6 drives are reported as being down in Veritas Device Monitor. The 4 drives that are down are not the same every week. To get the backups going again, I have to shutdown the Veritas daemons, reboot the Library, reinventory the Library and Verites, then restart the backups that did not complete.

The following day, after some of the backups completed, some of the drives are down again, and I have to repeat the process.